APD High-Speed Transports: Evolution of Destroyer Conversions in WWII
As the United States prepared for and engaged in World War II, the demands of naval warfare evolved rapidly. While modern destroyers were joining the fleet, the U.S. Navy found a strategic need to repurpose older vessels for specialized roles. This led to the development of the APD, a designation for high-speed transports designed to carry fully equipped troops for assault landings.
These vessels were not built from the ground up as transports but were instead converted from existing destroyers and destroyer escorts. By sacrificing some speed and heavy armament, the Navy created a versatile platform capable of delivering infantry to hostile shores with greater speed than traditional transport ships.
Key Facts
- Purpose: Fast transport of fully equipped troops for assault landings.
- Origins: Converted from WWI-era "flush-deck" destroyers and WWII-era destroyer escorts (DEs).
- Major Classes: Included the early flush-deck conversions, the Charles Lawrence class, and the Crosley class.
- Capacity: Depending on the class, they could carry between 162 and 200 troops.
- Landing Craft: Utilized LCPLs, LCPRs, and LCVPs to ferry troops from ship to shore.
The "Flush-Deck" Conversions
The first generation of APDs (APD-1 through APD-36) utilized "flush-deck" destroyers built during and after World War I. This group consisted of one Caldwell-class, 17 Wickes-class, and 14 Clemson-class vessels. Some of these ships had previously served as aircraft tenders before being converted to high-speed transports.
To make room for troops, the Navy removed two of the four forward boilers and their corresponding smokestacks. While this reduced the top speed to 25 knots (46 km/h), it created sufficient space to accommodate 200 troops in the former engine areas.
Armament and Equipment Changes
The original heavy armament—four 4"/50 low-angle guns, one 3"/23 anti-aircraft gun, and twelve 21-inch torpedo tubes—was stripped away. In its place, the Navy installed three modern 3"/50 dual-purpose guns, one 40 mm AA gun, and five 20 mm AA guns. For anti-submarine warfare, they carried two depth charge racks and up to six K-gun depth charge throwers.
The most critical change was the removal of torpedo mounts to make room for four davit-mounted LCPLs (Landing Craft Personnel, Large). These were later upgraded to LCPRs (Landing Craft Personnel, Ramped), which featured a bow ramp for easier troop deployment.
Destroyer Escort (DE) Conversions
As the war progressed, the Navy began converting newer destroyer escorts (DEs) into APDs. These conversions provided more modern hulls and updated systems compared to the WWI-era flush-deckers.
The Charles Lawrence Class
The second group of APDs consisted of 43 Buckley-class destroyer escorts built between 1943 and 1945, known as the Charles Lawrence class. The superstructure was expanded to house 162 troops.
The armament was significantly upgraded from the original Buckley-class configuration. The three 3"/50 DP guns and twin 40 mm mount were replaced by one powerful 5"/38 DP gun and six 40 mm AA guns in three twin mounts, while retaining the original six 20mm AA guns. These ships carried two depth charge racks, up to eight K-guns, and typically four LCVPs (Landing Craft Vehicle and Personnel) in a stacked davit configuration.
The Crosley Class
The third group comprised 51 Rudderow-class destroyer escorts built between 1943 and 1945. Known as the Crosley class, almost all of these vessels were converted while they were still under construction.
The Crosley class followed the same conversion specifications as the Charles Lawrence class, with one primary physical difference: they retained the original Rudderow low bridge, whereas the Buckley-based conversions featured a higher bridge.
Comparison of APD Conversion Classes
| Feature | Flush-Deck (Caldwell/Wickes/Clemson) | Charles Lawrence (Buckley) | Crosley (Rudderow) |
|---|---|---|---|
| Troop Capacity | 200 | 162 | 162 |
| Primary Gun | 3"/50 Dual-Purpose | 5"/38 Dual-Purpose | 5"/38 Dual-Purpose |
| Landing Craft | LCPL / LCPR | LCVP | LCVP |
| Bridge Height | Standard | High | Low |
| Origin | WWI Destroyers | WWII Destroyer Escorts | WWII Destroyer Escorts |
Frequently Asked Questions
What does APD stand for in a naval context?
APD is the hull classification symbol for a high-speed transport, typically a destroyer or destroyer escort converted to carry troops and landing craft for assault missions.
Why were boilers removed from the flush-deck destroyers?
Two of the four boilers were removed to create enough internal space to house 200 troops in the areas previously occupied by the engines.
What is the difference between the Charles Lawrence and Crosley classes?
While both were converted from destroyer escorts with similar armament and troop capacity, the Crosley class retained the low bridge of the Rudderow-class, while the Charles Lawrence class had the higher bridge of the Buckley-class.
What types of landing craft were used by APDs?
Early conversions used LCPLs (Landing Craft Personnel, Large) and later LCPRs (Landing Craft Personnel, Ramped). Later DE conversions used LCVPs (Landing Craft Vehicle and Personnel).
How did the conversion affect the speed of the flush-deck destroyers?
The removal of two boilers reduced the top speed of these vessels to 25 knots (46 km/h).